We propose to develop a system for real-time interactive magnetic reso- nance (MR) vascular imaging. The principal technique to be developed is real-time interactive color flow phase difference imaging. We hypothesize that this method and its variants can be developed to provide an efficient method for rapid assessment of vascular morphology and quantitative flow information. Work will be done in three areas: 1. Image Acquisition Physics. Three general methods will be studied, all with phase difference velocity estimation. Short TR gradient echo pulse sequences will be developed for high spatial resolution imaging of time-averaged flow at image rates of 1 Hz. Echo-planar methods will be developed to provide image rates of 5-10 Hz. Line scan techniques will be developed for temporal resolution in the 25-50 Hz range. Theory, simulations, and experiments will be performed to relate the reconstructed vascular signal to the actual blood velocity waveform and volume flow rate. Limits of sensitivity, resolution, accuracy, and precision will be determined. 2. High Speed Instrumentation. Instrumentation will be devised to enable instant reconstruction of data acquired using any of the above tech- niques. Color velocity maps will be overlaid on magnitude images at real-time rates. Interactive techniques will be developed to facilitate adjustment of scan parameters, such as image plane angulation, which affect image quality. Quantitative flow data will be determined at 25 Hz rates in real time. 3. In Vivo Assessment. The techniques will be evaluated in the assess- ment of vascular flow in the upper abdomen of normal volunteers. We believe that this work will lead to the first real-time interactive MR vascular imaging system, and that our previous experience in real-time acquisition and reconstruction uniquely qualifies us to conduct these studies.